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Installation and Configuration Manual 57
Calculated Parameters
Safety Certification Return PolicyProduct DataCalculated Parameters
ρ
v
= ρ
t
- [ K20 + K21*X + K22*X
2
] [5]
where:
• ρ
v
= Viscosity-corrected density (kg/m
3
)
• ρ
t
= Temperature-corrected density (kg/m
3
)
•X= 1/Q
2
(inverse square of the quality factor)
• K20, K21, K22 = Meter calibration constants for each calibrated range
Note: Viscosity correction on indicated density is not needed where the fluid viscosity is less than
100 cP as the effect may be considered negligible.
A.3.4 Pressure correction
The meter design is such that the influence of the line pressure on the indicated density measurement
is a negligible amount and can be ignored.
A.3.5
Velocity Of Sound correction equation
If the Velocity Of Sound (VOS) of the process fluid deviates substantially from the optimised
VOS/density profile shown in Figure A-1, it may be desirable to apply a correction. This may be
achieved by a simple introduction of an offset using the data from Figure A-1. Adjustment of the
value of K0 in the general density equation will achieve this. Alternatively, the following correction
equations may be used:
ρ
vos
= ρ
v
* [ 1 + ( 24.0E+06 / (ρ
v
+ 2900) ) * (
1
/ V
C
2
-
1
/ V
A
2
) ] [6]
Where:
• ρ
vos
= VOS-corrected density (kgm
-3
)
• ρ
v
= Viscosity-corrected density (kgm
-3
)
•V
C
= Calibration VOS (m/s)
•V
A
= Actual fluid VOS (m/s)
V
C
may be obtained direct from Figure A-1 or may be calculated as follows:
•V
C
= 64.1 + 1.414 * ρ
v
– for ρ
v
of 300 kg/m
3
to 1100kg/m
3
[7]
•V
C
= 2346 - 0.660 * ρ
v
– for ρ
v
of 1100 kg/m
3
to 1600kg/m
3
[8]
The value of V
C
is calculated by the Signal Converter when VOS-correction is applied in the software.